Auto-refractor and phoropter are commonly used for providing refraction prescription for eyeglass or contact lenses. An auto-refractor is used to produce objective measurement of eye spherical defocus power, cylinder power and cylinder axis. A phoropter is used to refine the measurement of auto-refractor through subjective response from the patients. The auto-refractor and phoropter are typically stand-alone instruments, and they require different sitting and alignment to perform the measurements. Also, a phoropter displays a number of trial lenses along the viewing path of each subject eye, and relies on response from the patient to identify the optimal refraction correction and thus the patient's prescription. Typically it takes 10 to 30 minutes to make a thorough refraction measurement with the common practices of auto-refractor and phoropter.
An auto-refractor typically measures one eye at a time and directs the subject eye looking at a fixation target inside the instrument. Instrument myopia, due to accommodating and fixating at an internal target, is commonly an issue limiting measurement accuracy and reliability.
An auto-phoropter is a good advancement from a phoropter, equipped with a control box and motorized mechanism to change trial lenses. An auto-phoropter is basically a motorized phoropter, which employs multiple sets of trial lenses to produce refraction correction for sphere and astigmatism. The measurement procedure via auto-refractor and auto-phoropter is still elaborating and time consuming.